1. Field of the Invention
The present invention relates to a rice polisher (rice polishing section or rice washing section) for conducting preprocessing to produce so-called “pre-polished rice” (pre-polished processed rice, dried washed rice, or processed rice) and with which it is possible to readily cook rice by only adding water, without the need to wash rice (i.e., to polish rice) before cooking the rice, and that has good preservability. The present invention further relates to pre-polished rice producing apparatus (pre-polished rice processing apparatus) a pre-polished rice producing facility comprising the rice polisher, and to a leveling device for leveling grains supplied on a receiving surface of a receiving member.
2. Description of the Related Art
When white rice (polished rice, raw material rice or raw material white rice) is washed in water by an ordinary method, water permeates the polished rice and the water content of the rice increases, whereby the rice becomes subject to mold growth or decomposition. Thus, pre-polished rice that can be handled in the same manner as ordinary polished rice cannot be obtained. Alternatively, when polished rice whose water content has been increased due to being polished in water is dried, the starch layer of the polished rice that has absorbed water and expanded shrinks upon being dried (see, for instance, Japanese Patent Application Publication (JP-B) No. 3-36496). Thus, when the polished white rice is dried, the surface of the starch layer of the polished white rice abruptly shrinks, whereby tension is created in the surface layer and the rice cracks. Polished rice that has sustained cracking absorbs a high volume of water during cooking, whereby the rice expands unevenly and a high volume of starch particle is released from the crack. It is well known that this results in rice having inferior taste.
JP-B No. 7-106321 discloses a pre-polished rice producing apparatus comprising a transversal rice polishing section including an agitating cylinder and an agitating roll for receiving polishing water (may also be called cleansing (polishing or washing) water or rice polishing (washing) water) for cleaning (washing or polishing) rice, and a rinsing-dehydrating section for dehydrating the rice polished (washed) while rinsing the rice in rinsing water supplied thereto.
However, according to this pre-polished rice producing apparatus, there is a problem in that a large amount of water must be used because water is needed for both the cleaning step and the rinsing step. Use of a large amount of water not only results in swelling water bills, but also means that a large amount of polluted water (polished-waste water, washed-waste water, discharge water or drain water) is discharged, whereby companies are obliged to use large and expensive water-purifying plants as stipulated by bylaws for the prevention of environmental pollution. Thus, this has become a big concern in the rice industry.
Japanese Patent Application Laid-Open (JP-A) No. 11-42056 discloses a pre-polished rice producing apparatus comprising a rice-hulling (milling) apparatus of an upright type, in which polished rice with washing water is moved downward by a supply screw and then moved back upward by a reverse screw, during which the rice undergoes an agitation and hulling (milling) process, and the processed rice is discharged from a lower portion.
However, according to this pre-polished rice producing apparatus, the polishing water is flown downwardly and the rice is moved downwardly in the same direction as the water flow, and the polished rice is discharged from the lower portion. Thus, although water is clear in a first step (upper portion) of the rice polishing, the water becomes dirty in a last finishing step (lower portion) of the polishing process. Therefore, even if the next dehydrating process provides an efficient dehydration, aleurone residue (waste water) will stay on the rice, posing a problem of deteriorated taste.
In another pre-polished rice producing apparatus (a wet type pre-polished rice producing apparatus), a rice polishing section is provided. Raw material rice (polished rice) supplied is agitated with polishing water in the rice polishing section, separating from the surface of the raw material rice such impurities as aleurone residue (i.e., liquid-like, extremely sticky mixture containing oil, protein and sugar included in the aleurone layer (layer of aleurone) which is the lowest layer of rice bran layers of brown rice). The separated matter is solved in the polishing water. Further, this pre-polished rice producing apparatus is provided with a dehydrating section. The raw material rice that has undergone the polishing process is supplied to the dehydrating section for dehydration.
Further, this pre-polished rice producing apparatus comprises a drying section. The drying section is provided with a drying disc. The raw material rice that has undergone the dehydrating process is supplied onto the drying disc, and a warm wind is supplied to the raw material rice to thereby dry the raw material rice.
With the above described processes, the pre-polished rice producing apparatus processes the raw material rice in the rice-polishing process, thereby producing a processed rice (the raw material rice dried at the drying section).
It should be noted here that, in general, water content increase in the pre-polished rice with respect to water content in the raw material rice (typically from 14 weight percent to 15 weight percent) should preferably be within plus 0.5 weight percent. Further, the water content of the polished rice should preferably be the same as in the raw material rice, i.e., in the range from 14 weight percent to 15 weight percent.
The reason for this is that a water content increase of plus 0.5 weight percent or greater in the pre-polished rice over the water content in the raw material rice is a result of excessive permeation of dirty polishing water (hereinafter called “waste water” (same as discharge water or drain water)) containing the aleurone residue at the time of rice polishing in the rice polishing section. The pre-polished rice permeated by such a large amount of the waste water does not taste good.
Further, if the water content in the pre-polished rice is less than 14 weight percent, the polished rice becomes subject to cracking on its surface, whereby the polished rice absorbs a high volume of water during cooking, resulting in uneven expansion or release of a high volume of starch particles from the crack. Such a cooking process described as above will make the cooked rice extremely low in quality and poor in taste.
On the other hand, if the water content in the polished rice is greater than 15 weight percent, the rice becomes subject to mold growth or decomposition, becoming poor in preservability.
However, according to the pre-polished rice producing apparatus as described above, an extent of the drying at the drying section fluctuates depending on the temperature and moisture of an atmosphere in the drying section, and amount of flow of the polished rice. Therefore, it is difficult to adjust the water content of the pre-polished rice.
It should further be noted here that in general, it is possible to improve quality of the wash-processed rice by controlling the water content difference between the wash-processed rice and a raw material rice within ±0.2 weight percent. In order to achieve this, according to the above described pre-polished rice producing apparatus, a human operator manually samples the raw material rice before the ready-to-cook processing and the processed rice after the ready-to-cook processing, and measures the water content in both. Based on the results of the measurements, the human operator manually changes the amount of supply of the raw material rice to the rice polishing section, the temperature of the warm wind supplied to the drying section, the amount of the warm wind to be supplied, and rotating speed of the drying disc, in order to adjust the water content in the processed rice.
However, according to the pre-polished rice producing apparatus, it is difficult to constantly produce the processed rice of a high quality, because the human operator will only measure the water content in the manually sampled processed rice and the raw material rice before the ready-to-cook processing as has been described above.
Further, the operator has to measure the water content in the raw material rice and the processed rice, and in addition, to constantly monitor operating status of the pre-polished rice producing apparatus for the adjustment of the water content in the processed rice. This poses a problem that the operator's task is complex.
Still further, according to a pre-polished rice producing apparatus such as the one described above, the rice polishing section and the dehydrating section in particular are fixed to a frame of the apparatus. Therefore, when performing a maintenance operation such as cleaning or polishing of the rice polishing section and the dehydrating section, a major dismantling and rebuilding procedures must be performed to most of the rice polishing section and the dehydrating section (or the entire portion thereof depending on the structure of the rice polishing section and the dehydrating section). Further, the dismantling and the rebuilding processes of the rice polishing section and the dehydrating section require a multiplicity of disassembling and reassembling steps which must be followed truthfully in a given order. This means that a huge amount of time and labor must be spent for the maintenance of the rice polishing section and the dehydrating section, making difficult the maintenance of the pre-polished rice producing apparatus.
Further, in order to properly perform the maintenance of the rice polishing section and the dehydrating section (including disassembling and reassembling of each component in the rice polishing section and the dehydrating section), the rice polishing section and the dehydrating section must have a size large enough to allow access. This creates another problem that the pre-polished rice producing apparatus tends to be unnecessarily large.
In general, in food processing machinery that uses water, it is absolutely necessary to clean the machine every time the operation is finished. The same principle applies to a pre-polished rice producing apparatus, and it is specifically necessary to clean inside of the rice polishing section including removal of residual rice (raw material white rice) at each end of the operation. In order to do such an internal cleaning of the rice polishing section as the above, the rice polishing section must usually be disassembled for the cleaning, and then reassembled. Otherwise, if the rice polishing section incorporates a shutter for example which can open and close the inside of the rice polishing section, the inside of the rice polishing section must be opened by the shutter for the cleaning, making the cleaning more complex. For these reasons, there is a desire for automated cleaning of the inside of the rice polishing section.
Further, a development is underway, in which a drying section has a drying disc above which a predetermined number of leveling plates are provided. According to a pre-polished rice producing apparatus as this, by leveling the polished rice on the drying disc by the leveling plates, it becomes possible to prevent uneven drying of the polished rice.
However, the amount of supply of the polished rice to the rice polishing section and the mount of dried polished rice at the drying section (the amount of discharge of the polished rice from the dehydrating section) can change from time to time depending on the cultivator and characteristics (such as grain size, ratio of chipped or cracked rice inclusion and so on) of the polished rice.
Under such a situation as above, if the amount of the dried polished rice at the drying section is too large, the polished rice overflows from the leveling plates. On the other hand, if the mount of the dried polished rice at the drying section is too small, the polished rice leveled by the leveling plates is not flat but has recesses. In any of the cases, the polished rice on the net cannot be leveled by the leveling plates, leading to uneven drying of the polished rice, potentially resulting in deterioration in the quality of the polished rice.
Further, if the polished rice supplied onto the drying disc in the drying section is not leveled uniformly over its entire surface to a uniform thickness, result is uneven drying of the polished rice as well as decreased drying efficiency. This leads to a problem of inability to obtain the pre-polished rice of a uniform quality in which there is no excessive fluctuation in the water content.
Still further, in order to obtain the pre-polished rice of a uniform quality in which there is no excessive fluctuation in the water content, from the pre-polished rice producing apparatus as has been described, it is preferable that the pre-polished rice producing apparatus be installed in an environment of stable temperature and humidity, and the pre-polished rice producing apparatus be operated under a stable environment in which temperature and humidity in the atmosphere (ambient air) are maintained within a certain constant range.
However, if a special air-conditioning equipment and so on are to be installed in order to maintain the constant environmental conditions (temperature and humidity) in the atmosphere (ambient air) in the place of installation of the pre-polished rice producing apparatus, an extremely high expense must be prepared for the equipment and facility.